The experiments employ a picosecond laser and time-resolved single photon counting detection. To study the photon paths, a screen is positioned inside a glass fish tank contained 1 micron polystyrene beads. The screen was used to probe the photon paths within the scattering medium. By varying the position of the screen in the medium, the time-resolved photon path distribution can be mapped out. The existence of well-defined time-resolved photon paths demonstrated by these experiments provides the basis for a three-dimensional optical tomographic scheme.